Brachiation

Brachiation, in animal behaviour, specialized form of arboreal locomotion in which movement is accomplished by swinging from one hold to another by the arms. The process is highly developed in the gibbon and siamang, which are anatomically adapted for it in the length of their forelimbs, their long hooklike fingers, and the mobility of their shoulder joints. The South American spider monkey, considered a semibrachiator, uses its prehensile tail as a third arm. Spider monkeys both run along branches and swing from them.

Because bipedal locomotion is the terrestrial form of movement in the true brachiators, some researchers believe that the human species may have evolved from a protobrachiator. Other researchers have tried to demonstrate that the so-called knuckle-walking apes (e.g., the gorilla) are descended from brachiating ancestors. They base this theory on the characteristically long arms and curved fingers of knuckle-walkers.

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in zoology, any mammal of the group that includes the lemurs, lorises, tarsiers, monkeys, apes, and humans. The order Primates, with its 300 or more species, is the third most diverse order of mammal s, after rodents (Rodentia) and bats (Chiroptera). Although there are some notable variations...

large, extremely agile monkey that lives in forests from southern Mexico through Central and South America to Brazil. In spite of its thumbless hands, this lanky potbellied primate can move swiftly through the trees, using its long tail as a fifth limb. The seven species of true spider monkeys are...

True brachiation (using the arms to swing from one place to another) is confined to a few species of primates, such as gibbons and spider monkeys. Because the body is suspended from a branch by the arms, brachiation is strictly foreleg locomotion. When the animal moves, it relaxes the grip of one hand, and the body pivots on the shoulder of the opposite arm and swings forward; then the free arm...